U.S. patent number 3,979,009 [Application Number 05/623,271] was granted by the patent office on 1976-09-07 for container bottom structure.
This patent grant is currently assigned to Kaiser Aluminum & Chemical Corporation. Invention is credited to Charles E. Walker.
United States Patent |
3,979,009 |
Walker |
September 7, 1976 |
Container bottom structure
Abstract
Improved bottom for a seamless metal container body wherein the
central portion of the bottom that includes a stiffening embossment
is joined to the other portions of the bottom in an improved manner
by a hinge-like section that permits selected and controlled
outward flexing or bulging of the bottom when the container is
sealed and subjected to internal pressures developed by the
contents of the container. Despite such outward flexing of the
bottom, the container still is provided with a stable bottom to
rest upon in its sealed and pressurized condition.
Inventors: |
Walker; Charles E. (Walnut
Creek, CA) |
Assignee: |
Kaiser Aluminum & Chemical
Corporation (Oakland, CA)
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Family
ID: |
27072349 |
Appl.
No.: |
05/623,271 |
Filed: |
October 17, 1975 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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560456 |
Mar 21, 1975 |
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Current U.S.
Class: |
220/609;
220/906 |
Current CPC
Class: |
B65D
1/46 (20130101); Y10S 220/906 (20130101) |
Current International
Class: |
B65D
1/40 (20060101); B65D 1/46 (20060101); B65D
007/42 () |
Field of
Search: |
;220/66,67,70
;215/1C |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1,061,643 |
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Jul 1959 |
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DT |
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532,675 |
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Nov 1954 |
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IT |
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528,006 |
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Oct 1940 |
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UK |
|
Primary Examiner: Price; William
Assistant Examiner: Marcus; Stephen
Attorney, Agent or Firm: Calrow; Paul E. Rhoades; John
S.
Parent Case Text
RELATED APPLICATION
This application is a continuation-in-part of my prior application
Ser. No. 560,456, filed Mar. 21, 1975, now abandoned.
Claims
What is claimed is:
1. A seamless metal container body comprised of a sidewall and a
bottom having controlled distention characteristics and formed
integrally with the lower extremity of the said sidewall, said
bottom having a centrally and inwardly disposed relatively shallow
dome-like depression the outer peripheral edge of which terminates
in a slight upwardly and outwardly projecting dished section, the
outer extremity of the said dished section merging with a generally
planar section, and the outer periphery of said planar section
merging with the sidewall, said planar section constituting at
least a substantial part of the total cross-sectional area of the
said bottom and the point of mergence of the dished section and
said generally planar section being comprised of a selectively
thinned and work hardened portion having distortion resistant
hoop-like strength characteristics, and said last mentioned portion
also acting as a relatively stiff hinge about which the central
part of the container bottom including the dished section is
allowed to flex selectively outwardly beyond the outermost plane of
the outer surface of the planar section when the overall bottom
flexes and is distended outwardly a controlled amount under the
influence of internal pressures within the container body.
2. A container body as set forth in claim 1, wherein said work
hardened portion comprises a coined portion.
3. A container body as set forth in claim 1 wherein said dished
section has a substantially inverted frusto-conical
configuration.
4. A container body as set forth in claim 1 wherein the dome-like
depression has a substantially spherical configuration.
5. A container body as set forth in claim 1, wherein the said
dome-like depression has a partial configuration approximating a
segment of sphere and a planar section joined to the terminal
bottom of the spherical segment.
6. A container body as set forth in claim 1 and made in the form of
a work hardened drawn and ironed can body.
7. A container body as set forth in claim 1 wherein said container
body comprises a work hardened impact extruded container body.
8. A container body as set forth in claim 1 wherein said work
hardened portion comprises a cross-sectionally curved and coined
portion and said container body is a drawn and ironed container
body.
9. A container body as set forth in claim 1 wherein said work
hardened portion comprises a cross-sectionally curved and coined
portion and said container body comprises an impact extruded
container body.
10. A container body as set forth in claim 1 wherein said work
hardened portion comprises a cross-sectionally curved and coined
portion and the major surface area of said bottom is provided by
said planar section.
11. A seamless cylindrical metal container body provided with a
sidewall and a bottom having controlled distention characteristics
and formed integrally with the lower extremity of the said
sidewall, said bottom being comprised of a centrally and inwardly
disposed relatively shallow dome-like depression which has at least
in part a substantially spherical configuration and the outer
peripheral edge of which terminates in a slightly upwardly and
outwardly projecting dished section, a generally planar section
which merges at its outer periphery with the said sidewall, said
planar section constituting a major part of the overall area of
said bottom of the container body and a selectively work hardened
and thinned cross-sectionally curved portion joining and
integrating said dished section with said planar section, said
curved portion also acting in the manner of a relatively stiff
secondary hinge about which the central part of the container
bottom including said dished section flexes outwardly and beyond
the outermost plane of the outer surface of the planar section when
the overall bottom flexes and is distended outwardly a controlled
amount under the influence of internal pressures within the
container body.
12. A container body as set forth in claim 11 wherein the dished
section has a slight inverted frusto-conicial configuration.
13. A container body as set forth in claim 11 wherein the thinned
curved portion comprises a coined section and the container body is
made in the form of an impact extruded container body.
14. A container body as set forth in claim 11 wherein the areas of
joindure between the dished section and the dome-like depression
and said dished section and said planar section also form primary
and secondary stabilizing ring portions.
15. The container body as set forth in claim 11 wherein the thinned
curved portion comprises a coined section.
16. A container body as set forth in claim 15 wherein said dished
section is frusto-conical.
17. A container body as set forth in claim 11 wherein said thinned
curved portion is comprised of a coined section, said dished
section has a slight inverted frusto-conical configuration and said
container body is a drawn and ironed container body made from a
hard tempered aluminum base alloy.
18. A container body as set forth in claim 17, wherein the areas of
joindure between the dished and the dome-like sections and the
dished and planar sections also form primary and secondary
stabilizing ring portions.
19. A container body as set forth in claim 11 wherein the thinned
curved portion comprises a coined section and wherein the container
body is made in the form of a drawn and ironed container body.
20. A container body as set forth in claim 19 wherein the areas of
joindure between the dished and dome-like depression and the dished
and planar sections also form primary and secondary stabilizing
ring portions.
21. A seamless drawn and ironed cylindrical container body of a
hard tempered aluminum base alloy provided with a sidewall and a
bottom having controlled distention characteristics and formed
integrally with the lower extremity of the said sidewall, said
bottom being comprised of a centrally and inwardly disposed
relatively shallow dome-like depression which has at least in part
a substantially spherical configuration and a planar base the outer
peripheral edge of which terminates in a slightly upwardly and
outwardly projecting dished section, a generally planar section
which merges at its outer periphery with the said sidewall, said
planar section constituting a major part of the overall area of
said bottom of the container body and a selectively work hardened
and thinned cross-sectionally and inwardly curved coined portion
joining and integrating said dished section with said planar
section, said curved portion also acting in the manner of a
relatively stiff secondary hinge about which the central part of
the bottom of the container body including said dished section
flexes outwardly and beyond the outermost plane of the outer
surface of the planar section when the overall bottom flexes and is
distended outwardly a controlled amount under the influence of
internal pressures within the container body.
Description
BACKGROUND OF THE INVENTION
The present invention relates to metal container bodies and more
particularly to metal container bodies of the seamless variety
comprised of a sidewall and a bottom formed integrally therewith.
The container bottom has an improved design to provide for
controlled flexing and distention of the same outwardly under the
influence of internal pressures generated by the contents of the
container or can after it has been closed and sealed.
In the past, a standard solution to the problem of providing a
seamless metal can body, such as an aerosol, beer or carbonated
beverage can body, with a bottom structure having the requisite
strength or internal pressure-resistant qualities, has called for
making substantially the entire bottom of such a can body in the
form of a dome-type panel that was recessed inwardly. Containers
provided with this general type of bottom structure are illustrated
in such prior art patents as U.S. Pat. Nos. 2,777,125; 3,029,507;
3,360,158; 3,416,702; 3,232,260; 3,730,383; 3,731,838; 3,693,828;
3,556,032; 3,603,275; 3,701,455; 3,782,315 and 3,785,311.
Alternately, seamless can bottoms have been provided with
conventional reinforcing beads or rings, such as are provided in
the seamless metal cans discussed at pages 26-31 of the Mar., 1952,
issue of the magazine entitled "Modern Metals" and at pages 20-23
of the Feb., 1959 issue of the magazine entitled "Florida Trend,"
and U.S. Pat. No. 3,312,098.
When a seamless metal can body having such a bottom structure was
fabricated in the past as, for example, that of U.S. Pat. No.
3,693,828, only the outer periphery of the can bottom was adapted
to contact the surface upon which the can rested whereby the can
had a substantial amount of stability in either a filled or empty
condition.
Despite the strength and stability provided by the inwardly
recessed and domed bottom in a seamless can body structure, such a
bottom ordinarily required a substantial metal thickness in the
starting metal blank so as to provide the requisite reservoir of
metal for properly forming the bottom and the adjacent sidewall
section in order to avoid deleteriously thinning of the bottom or
adjacent section of the sidewall in one or more areas to the point
that localized weakened areas resulted and the strength otherwise
provided by the domed bottom configuration was nullified.
Another disadvantage incident to the use of prior art seamless can
bodies provided with domed bottoms concerns the fact that the
deeper or larger the dome, the greater the volumetric loss in the
interior of the can. This volumetric loss had to be compensated for
either by increasing the length of the can sidewall and/or can
diameter with the consequent use of additional starting metal.
More recently, in an effort to utilize less metal material and
effect a savings in container cost, while at the same time still
utilizing a spherically or hemispherically domed bottom design for
the purposes of reinforcing the bottom of a seamless metal can
body, efforts have been made to provide a relatively deep or large
reinforcing dimple or bubble in the central portion of the seamless
can bottom and a relatively flattened area in the outer reaches of
such bottom. When a can body provided with such a bottom was filled
and sealed with a liquid under pressure, such as beer or a
carbonated beverage, the can bottom was permitted to flex or bulge
out in a selective fashion in a ring-like area adjacent the bubble.
In other words, the can bottom rather than resisting pressure was
allowed to flex outwardly in the direction of the pressure applied
thereto. Such a can, for example, is shown and discussed at page 96
of "Business Week" magazine for Nov. 23, 1974, and in U.S. Pat. No.
3,904,069, issued Sept. 9, 1975.
Even in this latter type of can bottom structure, however, because
of the relatively large size of the bubble used in the can bottom
as commercially manufactured and discussed in the aforementioned
Business Week magazine article, and when compared to the overall
bottom surface area of the can and because of the decrease in
capacity incident thereto, a substantial amount of metal is still
required in the final can body structure even though less starting
material may be used than that in the past. In other words, it can
still be necessary to provide an adequate reservoir of metal for
lengthening or increasing the diameter of the can sidewall as noted
previously in order to compensate for loss of capacity plus the
fabrication of a bubble or dome of the proper metal thickness and
strength. Thus, this last noted can bottom structure as well as
other and similar can bottom structures as shown in U.S. Pat. Nos.
3,369,694; 3,272,383; 3,359,841 and 3,572,271 can still be
objectionable as regards the amount of material required for the
bottom and sidewall structures to obtain the requisite strength,
volume, etc.
The instant invention is concerned with providing a seamless metal
can that is particularly advantageous as regards its being used to
dispense liquids maintained under pressure. It has an improved
bottom structure that can be made with a minimal metal thickness
consistent with other strength and volume requirements. The instant
container is also believed to have a relatively stable bottom when
filled with pressurized fluid, and even when flexed or distended in
the controlled manner to be described. The improved configuration
of the container bottom of the instant invention is such that where
the container is a drawn and ironed container it can be readily
formed in the tool pack of a standard draw and iron can bodymaker
and at the end of the ironing operation so that no separate and
costly doming operation need be used.
SUMMARY OF THE INVENTION
In providing an improved bottom for a seamless metal can body in
accordance with the instant invention, the central portion of the
bottom of the can is provided with a relatively shallow, inwardly
depressed dome or button-like section that can have the
configuration of a spheroid or spherical segment. The peripheral
edge of this depressed section advantageously terminates in a
somewhat upwardly and outwardly inclined ring-like dished section
and the outer extremity of this dished section merges with a
generally planar, ring-like section that also can project in a
somewhat upwardly and outwardly direction until it ultimately
terminates in and is integrally joined with the sidewall of the
can. This planar section constitutes at least a substantial and
preferably a major part of the total surface area of the can
bottom. The point of mergence of the dished section and the
generally planar section is preferably comprised of a selectively
thinned and work hardened, coined portion that has
distortion-resistant, hoop-like strength characteristics. This
coined portion advantageously acts in the manner of a stiff hinge
about which the central part of the can bottom comprised of a
dished section and button-like depression controllably pivots
outwardly until an edge of the dished section protrudes or extends
slightly beyond what constitutes the outermost plane of the outer
surface of the planar section, when the can bottom including the
central part of the can bottom flexes in the manner of a spring and
is distended outwardly under the influence of internal pressures
generated by the can's contents.
Since the dome or button-like depression is relatively shallow,
compared to prior art practices, no severe draw forming is required
to provide the same and less overall metal is needed to avoid
deleterious and excessive bottom wall and adjacent side-wall
section thinning. Such a bottom structure still has sufficient
strength characteristics to adequately meet the various internal
pressure requirements for commercially acceptable cans and, in
particular, those designed for beer and carbonated beverages.
The relatively shallow depth of the dome-like depression and other
adjacent shaped parts of the can bottom structure of the instant
invention also avoids the severe interior volume losses and the
necessity of increasing sidewall length and/or can cross-sectional
dimension to make up for such losses. The net result when applied
to a significant number of cans means substantial metal and cost
savings.
In the controlled flexing of the seamless container or can bottom
of the instant invention, when the top free edge of the can is
double seamed and sealed to a conventional end or to an end
provided with easy open features and then subjected to internal
bulging pressures, sufficient surface-to-surface contact is still
provided between the central part of the can bottom and a support
for the can to be effectively stabilized and resist tippage. When
the can is opened and internal pressure relieved, the bottom of the
can will relax and, in seeking to return to its original
as-fabricated shape will seek to contact the support over an
increased circumferential area and thus be further stabilized.
Although a seamless metal container body embodying the features of
the instant invention can be made from various metals, e.g. ferrous
metals such as steel, tin plate and black plate, it will be
discussed in the ensuing description with particular reference to
being manufactured from a light metal, such as aluminum, including
hard and extra hard tempered alloys thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partially sectioned and elevational view of an empty
seamless container body embodying the features of the instant
invention;
FIG. 2 is a plan view of the bottom of the container shown in FIG.
1 when taken along line 2--2 thereof;
FIG. 3 is a sectional view of the bottom and lower sidewall of the
container body of FIG. 1 when taken along line 3--3 thereof and
with the as-fabricated shape of the bottom being shown in full
lines and its shape when flexed under pressure being shown in
dotted lines;
FIG. 4 is a fragmentary sectional view taken within the boundary of
the circumscribing circle 4 of FIG. 3 and illustrates the flexed
shape of the bottom in full lines; and
FIG. 5 is a sectional view of the bottom and lower sidewall of a
prior art container provided with a conventional concavely domed
bottom panel or end .
DETAILED DESCRIPTION
With further reference to the drawings, a seamless metal container
body, such as the cylindrical seamless metal container body 10,
that embodies the features of the instant invention, can be
advantageously made in the form of a work hardened drawn or drawn
and ironed metal container, e.g. an aluminum container produced on
a draw and iron press of the type illustrated, for example, in U.S.
Pat. Nos. 3,289,453 or 3,496,756, or it can be an aluminum impact
extruded container or the like. When container body 10 is produced
on a draw and iron press, can bottom 12 integrally connected to the
sidewall 14 can be shaped on a standard and appropriate bottom
doming device located at the exit end of the press tooling. As
indicated particularly in FIGS. 2 through 4, container bottom 12 is
comprised of a relatively shallow, central and inwardly disposed
dome-like depression 16 that can be spheroidal, frusto-conical, or
in one preferred embodiment of the invention it can have a
configuration that approximates the segment of a sphere. The lower
peripheral wall section of button-like depression 16 can be
advantageously made in the form of a relatively planar wall
supporting segment 18 or simply the continuation of the arcuate
shape.
As indicated in FIG. 3, wall segment 18 is arranged at an
appropriate inside angle d, e.g. on the order of between 95.degree.
to 100.degree. to the adjacent dish-shaped and ring-like section 20
to which it is joined. Dish-shaped section 20 in the as-fabricated
can bottom structure of FIG. 3 projects outwardly away from
depression 16 and wall section 18 and in a slightly upward
direction until it merges with and is connected to a generally
planar bottom section 22 in the outer reaches of the bottom 12 by
way of the wall connecting section 24. Section 22 ultimately is
connected to the container sidewall 14 and this planar section 22
constitutes a substantial and preferably a major part of the total
area of the bottom 12. For example, it can constitute as much as 55
to 75% of the overall bottom surface area of the container body. In
one advantageous embodiment of the invention, section 22 can have a
slight downward inclination of a few degrees in its as-fabricated
condition relative to sidewall 14 so that it projects slightly
downwardly and inwardly from sidewall 14 and conversely slightly
upwardly and outwardly relative to section 20 as noted in FIGS. 3
and 4 instead of being disposed at a 90.degree. angle relative to
the sidewall 14.
The point of mergence 24 of the dish-shaped section 20, the latter
of which can have a somewhat inverted frusto-conical shape, is
comprised of a somewhat cross-sectionally and inwardly curved,
stepped and selectively work hardened and thinned coined portion
having distortion resistant, hoop-like strength characteristics.
The thinnest portion of section 24 preferably occurs at the point
of juncture between section 24 and section 20. As indicated
particularly in FIG. 4, this same stepped and coined portion during
the bottom forming operation is selectively deformed beyond the
elastiic limit of the metal in bottom 12 so as to set and position
dished section 20 in a substantially fully retracted position
relative to the bottom surface 28 of planar section 22 in the empty
and as-fabricated can body of FIGS. 1 and 3. This same somewhat
curved and coined portion 24, on the other hand, advantageously
acts as a relatively stiff hinge about which the central part of
the container bottom, which includes dished section 20 and the
shallow dimple 16 can flex and become distended outwardly under the
influence of the internal pressure generated by the container's
contents, etc. when the container has been sealed, so that the
primary annular stabilizing ring portion 26 formed at the junction
of can bottom sections 18 and 20 can then protrude slightly beyond
the outermost plane S that can be projected by the lowest point on
the outer surface 28 of section 22 and serve as a can support base,
all as indicated particularly in FIGS. 3 and 4.
With further reference to FIGS. 3 and 4, therefore, when internal
pressure is exerted upon the bottom 12 of a fully closed and sealed
can generally in the manner indicated by the arrows, the planar
section 22 as well as the central portion of the bottom made up of
sections 16, 18 and 20 will all flex outwardly. This flexing takes
place in a controlled fashion and in the manner illustrated in
dotted lines in FIG. 3 and full lines in FIG. 4 until as noted
previously the stabilizing ring portion 26 of bottom 12 moves
beyond the plane S that can be projected by the bottom surface 28
of planar section 22 and out to a new plane S' that can be
projected by ring portion 26 and then into contact with the surface
upon which the can is to rest. Control of the dimensions and shape
of depression 16 along with the amount of coining or work hardening
of section 24 all help to control the flexibility of the can bottom
and prevent any undesired and excessive outward bulging of the can
bottom. When the can is opened and internal pressure relieved, the
bottom of the can will relax and, as the overall bottom tends to
collapse and flex inwardly, sections 20 and 22 will tend to return
to their as-fabricated positions, with stabilizing ring portion 26
tending to retract inwardly of the aforesaid plane S' while the
outer secondary stabilizing ring portion 32 formed at the junction
of surface 28 and coined section 24 will seek to contact the
support and become the primary support base for the can 10 adjacent
coined section 24.
The aforesaid inward flexing and retraction will tend to occur even
in cases where coined section 24 may receive a slight permanent
deformation outwardly due to the outward distention of section 20
by the internal pressures within the sealed can. In other words,
depending upon the particular metal and the alloy and temper
thereof used for can body 10 there may or may not be a slight
outward permanent plastic deformation of coined section 24 under
pressure whereby stabilizing ring portion 26 will not be fully
restored to its initial as-fabricated position of rest upon the
relaxation of internal pressure, even though it will always seek to
be restored to such an initial position of rest.
In a further advantageous embodiment of the invention, secondary
stabilizing ring portion 32 functions in a unique fashion in
preventing tipping of the container because even when the unopened
and filled container is under pressure ring portion 32 will be
located slightly inwardly but a few fractions of an inch from the
level of primary stabilizing ring portion 26. In other words,
should the sealed and filled container body tend to tip for one or
more reasons, it will almost immediately come into contact with a
part of secondary stabilizing ring 32 and be restored to a position
of stability unless the tipping force is so great that the pivotal
action of the can is severe enough to cause the can to tip past
both secondary stabilizing ring portion 32 and the third
stabilizing ring portion 34 formed at the juncture 30 of bottom 12
and sidewall 14 and all concentrically arranged relative to ring
portion 26.
During the flexing of the can bottom, it is to be understood that
the amount or thickness of metal present at the point of merger or
juncture between section 22 and wall 14 will determine the degree
of stiffness of this primary hinge point for bottom 12. In a
preferred embodiment of the invention enough metal should be
present to allow section 22 to distend slightly outwardly under
pressure followed substantially immediately by a slightly further
outward distention of the central part of the can bottom. The area
of this central part of the can bottom and containing sections 16,
18 and 20 is indicated by the letter B of FIGS. 1 and 2, the bottom
area formed by depressed segments 16 and 18 by the letter A and the
overall area of can bottom by the letter C. In the flexing of
bottom 12, juncture point 30 can be considered a first or primary
hinge and section 24 a secondary hinge.
From the above description, it will be seen that the shallow
structure and the lack of severe deformation of the can bottom,
except in the selectively thinned or coined area 24 mean that a
minimal amount of metal material is required in the bottom of the
can to form the various concentrically disposed sections 24, 20, 18
and 16 and sidewall 14 in accordance with a given can requirement
as to strength and capacity. For example, whereas in the past a
commercially acceptable 12 ounce beverage can made from a 3004
series aluminum alloy as designated by the Aluminum Association and
of an extra hard or H-19 temper would ordinarily have a nominal
bottom wall thickness of 0.016 inch plus or minus the usual
tolerances, the same 12 ounce can provided with the instant bottom
design, and when made from the same aluminum alloy and temper may
now be made with a nominal bottom wall thickness of 0.014 inch. In
such instance, the controlled coined area 24 may have a thickness
of about 0.010 inch in the thinnest part thereof and the top of the
button-like depression 16 which ordinarily is the thinnest overall
part of the bottom can have a thickness of about 0.009 inch.
Although the savings in metal material due to the improved bottom
structure is believed to be significant, additional savings can be
realized in manufacturing costs by the use of simplified washing
and can coating procedures required for a can of the instant
invention. For example, in contrast to the expensive procedures
required to uniformly coat the intricate inside bottom surface of
the can of FIG. 5, the configuration of the bottom of the instant
can lends itself to being washed and coated by relatively
uncomplicated equipment and methods as well as to being formed on a
draw and iron press.
An advantageous embodiment of the invention has been described.
* * * * *